The present invention relates to a coloring device used in combination with a monochromatic display device to form a color image display device or in combination with a monochromatic image pick-up device to form a color image pick-up device.
FIG. 1 shows a conventional color image display device using a monochromatic image display, such as a black-and-white CRT (cathode-ray tube).
As illustrated, it includes a black-and-white CRT 10 and a coloring device 20 including a filter assembly 22 and a D.C. (direct current) rotary motor 30. The filter assembly 22 has a disk-shaped rotary filter 24 formed of color filter sections FR, FG and FB permitting transmission of light of red (R), green (G) and blue (B) and each extending over an angular range of 120, as illustrated in FIG. 2. In other words, the disk-shaped rotary filter 24 is divided by radially extending lines 24rg, 24gb and 24br into three equal sectors FR, FG and FB, each having a vertex angle of 120.degree. and respectively serving as color filters for red (R), green (G) and blue (B). The rotary filter 24 is fixed by a connection member 26 to a motor shaft 32 of the motor 30, and is rotated by the motor 30.
As the motor 30 rotates, the filter sections FR, FG and FB sequentially pass over a screen 12 of the CRT 10.
A rotation sensor 40, which may comprise a Hall element, detects the rotation phase of the rotary filter 24. A magnet 50 is attached to the shaft 32 of the motor 30 and serves as a detection member (member to be detected by a sensor) by the rotation sensor 40. That is, each time the shaft 32 rotates, the magnet 50 passes by the sensor 40, which thereby detects the passage of the magnet 50, on the basis of the magnetic field emanating from the magnet 50, and generates a rotation sync pulse P.
The rotation sync pulse P is supplied to a control device 60. The control device 60 also receives a vertical sync signal VD directly and also via a frequency converter 62. The frequency converter 62 converts the vertical sync signal VD into a triple-frequency vertical signal V3 having a frequency three times that of the vertical sync signal VD.
The control device 60 supplies the motor 30 with a drive signal. The rotation of the motor 30 is controlled such that the rotary fitter 24 rotates once per vertical. period, and the rotation sync pulse P is produced at a constant phase angle relative to the vertical sync signal VD.
Another frequency converter 68 converts a horizontal sync signal HD into a triple-frequency horizontal signal H3 having a frequency three times that of the horizontal sync signal HD.
Image signal memories 66R, 66G and 66B receive and store color image signals SR, SG and SB of red, green and blue together forming a color image.
The memories 66R, 66G and 66B are supplied with a horizontal sync signal HD and the vertical sync signal VD as reference sync signals for writing, and are supplied with the triple-frequency horizontal signal H3 and the triple-frequency vertical signal V3, as reference sync signals for reading.
The color image signals SR, SG and SB are sequentially written in the memories 66R, 66G and 66B. The color image signals for one field are stored at a time, and the color image signals SR, SG and SB for one field are repeatedly read three times, each in a period of one third of the vertical period. The writing and reading are carried out concurrently. Thus, color image signals SR3, SG3 and SB3 of a triple rate, and repeated three times, each for a period of one third of the vertical period, are obtained from the memories 66R, 66G and 66B.
FIGS. 3A to 3C show the color image signals SR, SG and SB supplied to the memories 66R, 66G and 66B, and FIGS. 4A to 4C show the color image signals SR3, SG3 and SB3 output from the memories 66R, 66G, and 66B. The waveforms are shown schematically to facilitate distinction between the three color image signals. The reference marks R1, R2, G1, G2, B1 and B2 show that in reading the same color image signals are repeatedly read three times, at a triple rate. For instance, the color image signal R1 of red for one field is written over one vertical period, and is read three times, each in one third of a vertical period.
The triple-rate color image signals SR3, SG3 and SB3 output from the memories 66R, 66G and 66B are supplied to the multiplexer 64, which is controlled by a switching signal S supplied in synchronism with the signal V3. As a result, one of the color image signals SR3, SB3 and SB3 corresponding to the filter section FR, FG or FB which is passing over the screen 12 of the CRT 10 is supplied from the multiplexer 64 to the CRT 10.
The triple-frequency signal H3 is supplied from the frequency converter 68 to a horizontal deflection circuit 70, and the triple-frequency signal V3 is supplied from the frequency converter 62 to the vertical deflection circuit 72. Horizontal and vertical deflection signals are supplied from the deflection circuits 70 and 72 to horizontal and vertical deflection coils (not shown) in the CRT 10. The CRT 10 therefore conducts horizontal and vertical deflection scanning at a rate three times that of ordinary scanning.
FIGS. 5A to 5D show the relationship between the rotation phase of the rotary filter 24, the scan line SL of the CRT 10 and the switching of the multiplexer 64.
The multiplexer 64 is controlled to operate in synchronism with the triple-frequency vertical signal V3 as described above, and is made to select the color image signals corresponding to the filter section that is passing over the screen 12 of the CRT 10, in accordance with the rotation sync pulse P. The multiplexing is so made that when the boundary 24br between the filter sections FB and FR is passing over the center (the midpoint in the vertical direction) of the screen 12 of the CRT 10, supply of the blue color image signal SB3 for one field to the CRT 10 is terminated and supply of the red color image signal SR3 for one field is commenced (FIG. 5A). Similarly, when the boundary 24rg between the filter sections FR and FG is passing over the center of the screen 12 of the CRT 10, one third of the vertical period later, supply of the red color image signal SR3 for one field to the CRT 10 is terminated and supply of the green color image signal SG3 for one field is commenced (FIG. 5D). Similarly, when the boundary 24gb between the filter section FG and FB is passing over the center of the screen 12 of the CRT 10, one third of the vertical period later, supply of the green color image signal SG3 for one field to the CRT 10 is terminated and supply of the blue color image signal SB3 for one field is commenced (not illustrated)
With the above configuration, the triple-frequency signals SR3, SG3 and SB3 are sequentially supplied from the multiplexer 64 to the CRT 10, while the horizontal and the vertical deflection scans are conducted at a triple rate, so black-and-white images due to the color image signals SR3, SG3 and SB3 are sequentially displayed on the screen 12, each in a period one third that of the vertical period.
As described above, the selection between the color image signals SR3, SG3 and SB3 is made in conformity with the filter sections FR, FG and FB of the rotary filter 24 which is passing over the screen 12 of the CRT 10, so that as the image due to the color image signal SR3, SG3 or SB3 is displayed on the screen 12, the corresponding filter section FR, FG or FB is positioned over the screen 12 of the CRT 10.
Accordingly, red, green and blue images by virtue of the color image signals SR3, SG3 and SB3 are obtained through the filter sections FR, FG and FB of the rotary filter 24, at the one-third vertical period. The net effect is that a color image is seen to the viewer observing the image through the filter sections FR, FG and FB.
Because the color image display device in the prior art is configured as described above, the space between the stator 33 and the rotor 35 combination of the motor 30 and the filter sections FR, FG and FB of the rotary filter 24 must be wide to permit disposition of the rotation sensor 40 between the stator 33/rotor 35 combination and the rotary filter 24, and this imposes a limitation on size reduction.
Another problem is that the speed at which the rotary filter 24 must be rotated is high. That is, the drive motor 30 is required to rotate the rotary filter 24 at the frequency of the vertical sync signal. The voltage applied to the motor must therefore be high, and the power consumption is large.
In another example of the prior art shown in FIGS. 6 and 7, the rotary filter 124 is in the form of a truncated circular cone and is radially divided, into equal parts, which form filter sections of red, green and blue. The conical rotary filter 124 has its small-diameter end 124a mounted to the output shaft 132 of a motor 130, and is provided so that it can rotate about its axis 124x of the cone in the direction of the arrow 124r. As shown in FIG. 6, the screen 12 of the CRT 10 is provided to confront the outer conical surface of the rotary filter 124. By utilizing the space efficiently in this way, the size of the overall device can be reduced.
The arrangement of FIGS. 6 and 7 suffers from the same problem as the arrangement of FIG. 1 if a magnet for detection of the rotation phase is attached to the shaft 132.
Another problem is that the conical rotary filter 124 with three sections having different filter characteristics is difficult to fabricate.
It is also possible to form a color image pick-up device by using the coloring device 20 and a monochromatic image sensor, such as a line sensor, but such an image pick-up device has similar problems.